Wireless communication devices have become smaller and more powerful as well as more capable. Increasingly users rely on wireless communication devices for mobile phone use as well as email and Internet access. At the same time, devices have become smaller in size. Devices such as cellular telephones, personal digital assistants (PDAs), laptop computers, and other similar devices provide reliable service with expanded coverage areas. Such devices may be referred to as mobile stations, stations, access terminals, user terminals, subscriber units, user equipments, and similar terms.
A wireless communication system may support communication for multiple wireless communication devices at the same time. In use, a wireless communication device may communicate with one or more base stations by transmissions on the uplink and downlink. Base stations may be referred to as access points, Node Bs, or other similar terms. The uplink or reverse link refers to the communication link from the wireless communication device to the base station, while the downlink or forward link refers to the communication from the base station to the wireless communication devices.
Wireless communication systems may be multiple access systems capable of supporting communication with multiple users by sharing the available system resources, such as bandwidth and transmit power. Examples of such multiple access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, wideband code division multiple access (WCDMA) systems, global system for mobile (GSM) communication systems, enhanced data rates for GSM evolution (EDGE) systems, and orthogonal frequency division multiple access (OFDMA) systems.
Wireless devices, including mobile telephones are required to undergo testing to determine the amount of RF energy a user may be exposed to when using the device. In the U.S., the Federal Communications Commission (FCC) certifies mobile devices to ensure compatibility with requirements and user safety. The maximum power that a mobile device may use when transmitting is affected by the fact that users position the device against their head and body. The close proximity or contact is behind the FCC requirements setting limits on the specific absorption rate. SAR is defined as the power absorbed per unit mass of tissue in mW/g by regulatory bodies, including the FCC. Current FCC testing requirements allow for a finite separation distance between the smartphone and the torso portion of a human phantom. In the United States, the FCC limits SAR to 1.6 W/kg as averaged over any 1 gram of tissue for a localized exposure.
In the European Union the Comité Européen de Normalisation Électrotechnique (CENELEC), or European Committee for Electrotechnical Standardization. CENELEC limits SAR to 2 W/kg averaged over 10 grams of tissue for localized exposure. Maximum average power levels are used to determine SAR compliance. SAR values are specified by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) and are to be averaged over any six minute period. ICNIRP determines exposure limits for electromagnetic fields used by devices such as cell phones.
As mobile devices become more popular, and with increasing use of smartphones, users frequently run applications on the device. Applications may run in the background for a number of reasons, and users may be unaware that an application is running in the background. SAR limits may limit transmission when applications are running in the background and the SAR usage within the six minute window is close to the maximum. There is a need in the art for a method and apparatus to schedule background processes with knowledge of SAR measurements.